Antibiotic residues in foods are a major food safety concern. Health issues include bacterial resistance to drugs and allergic reactions. Food is tested worldwide for antibiotics and other contaminants. Immunochromatographic test devices, such as lateral flow test strips, are often used to perform such testing and are well known in the art. Examples of such devices and related methods are described in U.S. Pat. Nos. U.S. Pat. No. 7,410,808, issued Aug. 12, 2008 and U.S. Pat. No. 5,985,675, issued Nov. 16, 1999; U.S. Pat. No. 6,319,466, issued Nov. 20, 2001, and U.S. patent application Ser. No. 10/289,089, filed Nov. 6, 2002 (based on U.S. Provisional Application 60/332,877, filed Nov. 6, 2001); and U.S. patent application, the teachings of which are incorporated herein by this reference.
Lateral-flow test strips can be configured to detect one or more analytes in a fluid sample such as a milk sample. Such strips typically include a capture agent immobilized within a defined region of the test strip, variously referred to as a test line or a test zone and/or a control zone or control line. The capture agent of choice has binding affinity for a reagent that is in a mobile phase of the test strip. If the mobile-phase reagent is detectably labeled, a detectable signal can be generated within the region of the test strip in which the mobile-phase reagent binds to the capture agent.
The sensitivity and specificity of a test device or method relative to a particular analyte relates to the binding affinity between the analyte and a binder. If the binder and analyte have good affinity, analyte-binder complex will form readily. In the case of a multianalyte binder—a binder that has affinity to more than one analyte—the affinity of certain analytes to the binder may be different than others. In addition, the particular affinity of a particular analyte to a chosen binder may not reflect the desired detection level for that analyte. In those cases, it is desired to adjust the test sensitivity to the particular analyte. For example, U.S. Pat. No. 6,319,466 describes a test device and method for detecting an analyte at reduced sensitivity levels.
We describe herein a method and device for decreasing test sensitivity to one or more analytes for which a multianalyte binder is overly affinitive relative to the desired detection level for one or multiple analytes. If there is too much affinity, the test will be overly sensitive. By reducing the test sensitivity to such analytes, while either maintaining or increasing test sensitivity to another analyte to which the multianalyte binder has affinity, the test can be adapted to detect analytes at desired levels, such as desired regulatory levels.